Burner assembly



July 24, 1962 E. J. TJERNLUND BURNER ASSEMBLY 4 Sheets-Sheet l Filed Oct. 29, 1958 4 SheeLs-SheerI 2 BURNER ASSEMBLY E. J. TJERNLUND `Iuly 24, 1962 Filed OCT. 29, 1958 D 5 N n .0 N RL R m Mn NR r Ew; mT J. m E

July 24, 1962 Y E. J. TJERNLUND 3,045,744

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July 24, 1962 E. J. TJE'RNLUND 3,045,744

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/zal 94 /so M# lrfaxweys United States Patet Filed'Oct. 29, 1958, Ser. No. 770,356 9 Claims. (Cl. 158-28) This invention relates to fuel burning apparatus, more specifically to improved multiple sta-ge burners'.

In heat exchanging systems wherein heat is provided to a load, such as heating-Ventilating systems, drying systems, etc., the thermal load quite often varies over a wide range, For example, in a heating-Ventilating system the thermal load varies with `atmospheric temperatures. Heat exchanging systems of the type just mentioned have been designed to compensate for varying loads by turning the burner on and off at predetermined temperatures, and by providing multiple selectively operable fuel nozzles in 'a single burner head. The just described load compensation methods create certain ineiciencies in the Iheat exchanging system which increase fuel consumption for B.t.u. output.

`A wasteful operation in any burner is Ithe ignition and extinguishment of the flame. Additionally, in the on-olf type of control, jus't mentioned, circulating fans, pumps, etc., often are indirectly controlled by burner operation through bonnet temperatures resulting in starting and stopping of these equipments. In `an effort to provide a more eilicient heat exchanging operation multiple fuel nozzles were provided in a single burner head. For example, two nozzles have been provided wherein the fuel injected from a first nozzle provides the low rate of heat exchanged and the fuel from the second nozzle is provided in addition to the lfuel from the lirst nozzle to provide a high rate of heat exchange. The fuel and -air are mixed in the same burner head resulting in varying fuel-air mixture velocities. The burner modulates the heat flow following the changing thermal load by switching between the two rates of heat exchange in yaddition to turning the burner `on and olf. This situation lgives rise to some inefficient combustion because of `an improper fuel-air mixture at either the high or low rate of heat exchange. Additionally the amount of air available in the burner 'head often remains constant, further contributing to an improper fuel-air mixture at either the low or high rate of heat exchange. At the low heat rate the fuel-air mixture velocity is often reduced thereby decreasing the burning eiciency.

If more rates of heat exchange are desired it is obvious to those skilled in the art that increased inefficiencies are created.

According to this invention a burner is provided which obviates the just `described diiculties. A plurality of burner heads, for example three, `are provided rather than three nozzles in 'a single burner head. `Additionally suitable combustion air and draft controls are provided to fur-ther enhance combustion chamber operation. Each burner head provides a passage for the combustion `air necessary to combine with the fuel it itself injects into the combustion chamber. At least Iall but one burner head may have an air valve controlling the combustion air How through said air passages; the air valve is opened only when -fuel is to be or is being provided to the burner head. Such a situation can create variations of air pressures on the inlet portions of the burner heads, thereby causing variations in air flow rates -through the just mentioned :air passages. This invention also eliminates this variation by providing controllable combustion lair retarding apparatus and controllable air bypass apparatus on the air supply to -substantially eliminate variations in inlet Iair pressures. Additionally to provide proper drafts for all levels of heat release, i.e., all levels "ice of combustion rates in the combustion chamber, a `draft controller is coupled to the just described combustion air controls thereby automatically coordinating draft with available combustion air.

Accordingly it is the prime object of this invention to provide a much improved multi-stage fuel burning apparatus.

It is another object of this invention to provide fuel burning apparatus with multiple selectively operable burner heads.

IIt is a further object of this invention to provide fuel burning apparatus having multiple burner heads wherein the amount of air provided to the combustion chamber is varied according to which burner heads are operating.

It is a still further object of this invention to provide apparatus as in the above objects having safety control means operable with one lburner head to control the operability of other burner heads.

It is another object of this invention to provide apparatu-s in conjunction with the first four objects of this invention for lbypassing the combustion air from nonoperating burner heads to the atmosphere.

It is still another object of this invention to provide coordinated combustion air, draft and fuel controls in a multi-stage heat exchanging system.

These and lother more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which- FIG. l is an end elevation of an exemplary burner assembly according to this invention as one would see the burner installed to lire into a combustion chamber of a furnace.

FIG. 2 is the corresponding plan view associated with FIG. 1.

FIG. 3 is a vertical section through the burner head portion of the burner assembly including the combustion air chamber, taken along line 3-3 of FIG. l.

FIG. 4 is a side elevation of the Iburner assembly looking from the right of FIGS. 1 `and 2.

FIG. 5 is a vertical section through the burner head assembly taken along line 5-5 of FIG. 3 looking toward the combustion chamber.

FIG. 6 illustrates exemplary operati-ng control means and burner sequencing means for use with the exemplary embodiment of this invention.

Referring no-w more particularly to the drawings reference numerals will be used to denote like parts and structural features in the different views and schematic diagram. In the figures numeral 10 generally denotes the burner head assembly including three burner heads, 12, 1.4 and 16. It is understood that any number of burner heads may be used in the burner head assembly, three heads tbeing used for illustrative purposes, no ylirnitatio-n thereto intended. Attached to the front of the burner head assembly, i.e., the portion of the assembly 10 for receiving the fuel and air as hereafter explained, is a combustion air chamber 18. Chamber 18 receives combustion `air through air duct 20 from air supply means indicated generally by numeral 22. In the exemplary embodiment of the invention a motor Z4 drives a centrifugal fa-n 26 forcing air from the atmosphere into duct 20. Centrifugal fan 26 may be coupled to motor 24 on common shaft 27 (FIG. 2). Additionally exhaust fan (FIG. 2) may also be coupled to the items 26 and 24 on shaft 27. Fan 30 provides an induced draft as hereafter explained tothe combustion chamber 32 indicated generally in the figures. Both fans 26 and 30 rotate counterclockwise. The whole just described assembly is suitalbly bolted to combustion chamber shroud 31.

Motor 24 drives fuel pump 34 by the pulley belt 36 mounted on pulley 38 axed to shaft 27 and on pulley 40. Pulley 40 is suitably fastened on shaft 42 of twostage fuel pump 34. Fuel may be provided to fuel pump 34 through inlet 35 in the usual manner. The output of pump 34 is essentially at constant pressure feeding the three fuel lines 44, 46, and 48. The just mentioned fuel lines feed three fuel valves S0, 52 and 54, respectively, which are selectively operable by the apparatus described in FIG. 6 to selectively provide fuel to burner heads 12, 14 and 16, respectively, as hereinbelow explained.

etailed description of the oper-ation of the exemplary lburner apparatus follows. The timing and control portion of the description will refer generally to FIG. 6 while the description of the effectuation of said timing and control will refer to the remaining figures. It is to be understood that the electrical schematic diagram o-f FIG. 6 represents components many of which are physically included in the burner assembly as shown in the remaining figures. For purposes of clarity the physical wiring is omitted from FIGS. l through even though the physical location of some of the `larger components indicated in FIG. 6 are pointed out. It is preferred that the operation of the burner assembly be under the control of temperature sensing devices, for example thermostats and bonnet controls, such as are well known in the heating arts. In FIG. 6 `thermostat 56 may be a conventional bimetallic strip operating switch 58 and is located in the space to be heated (not shown). rIlhe operation is such that switch 58 is closed when the ambient temperature about thermostat 56 is below a first predetermined temperature and open when said ambient temperature is above a second predetermined temperature. Therefore the switch 58 will close at a first temperature, cause the burner to come on, and will open at second predetermined temperature causing the burner to turn olf, as will be now explained.

Switch 58 is wired in series circuit with conventional *bonnet control 60 having switch 62. Control 60 operates in the manner described for thermostat 56, only the predetermined temperatures are in the bonnet (not shown) of the heat exchanger, i.e., that portion of a hot air furnace, for example, through which the air to be heated is passed. The just described series circuit is connected to relay 64 (see FIG. 4 for physical location) conveniently termed -a load relay, which when actuated indicates that a demand for heat is present, and to terminal 66 of flame indicating relay 68 (see FIG. 4 for physical location), the operation of which will be later explained.

The actuation of relay 64 will now be described. The circuits of FIG. 6 operates from 110 volt, 60 cycle current supplies connected through upper limit switch 70 in the usual manner. It is well known that the limit switch prevents the bonnet (not shown) from exceeding a high predetermined temperature to prevent damage to the heat exchanger (not shown). Switch 70 is normally closed and opens when the bonnet (not shown) reaches the first mentioned high temperature thereby turning off the burner. The neutral line of the 110 volt is grounded as indicated by ground 72, the hot side passing through switch 70 to line 74 to one terminal the primary winding of transformer 76, the other terminal being grounded. Line 78 being coupled to line 74 connects the hot side to the motor 24 and other components as hereafter explained.

Conventional direct constant current power supply 80 is coupled to line 74 and provides a plate supply voltage, for example +100 volts, to resistance 81 to energize relay 68. The power from supply 30 supplied through resistance 81 thence through relay 68 moves switch parts 86, 88 and 90 to the right. Of immediate concern is switch part 90 which is now closed. A circuit is now completed through the solenoid of relay 82 as follows: Line 92 through relay 82, thence over line 94 to terminal 96 on the secondary winding 98 of transformer 76. Power is inserted into this being described circuit from winding 98. The other end of secondary 98 is coupled over line 100 to terminal 202 of switch part 90, thus completing a circuit operable to actuate relay 82.

As relay 82 actuates, switch parts 102 and 106 close, switch part 102 forming a holding circuit having one terminal connected to line the other to relay 82 to keep relay 82 actuated as long as power is applied through limit switch 70. Switch part 106 couples amplifier 84 to power supply 80. Amplifier 84 is driven by photocell 108 which at this time is not providing either a voltage or current signal. Amplifier 84 is highly conductive and thereby provides a low impedance and lowers the voltage on resistance 81 substantially to ground reference potential which de-energizes relay 68. Amplifier 84 may be a conventional voltage amplifier providing a ground reference voltage output when photocell 108 is not detecting a flame as hereafter explained, and conversely presents a high impedance and provides a positive voltage output to relay 68 when said photocell is indicating a flame. A negative voltage may be applied to the control grid of relay puller amplifier 84 to make it non-conductive, i.e., not actuated, thereby allowing relay 68 to return to the original de-energized position, such as shown for the switch parts 86, 88 and 90 in FIG. 6. Power supply 80 may also supply D.C. voltages in the usual manner to operate amplier 84 through suitable connections (not shown).

With thermostat 56 and bonnet control 60 forming a closed series circuit through their respective switches, load relay 64 will be actuated. The circuit is from the said series circuit to line 110 thence through relay 64, through normally closed safety switch 1112 and over line 114 through switch part 102 which was closed as hereinabove described, and to line 100 coupled to the upper end of secondary winding 98, from terminal 96 on the lower end of winding 98 over line 94 through safety switch heating element 116 thence through switch part 86 (relay 68 was de-activated by switch part 106 closing), over terminal 66 and line 118 to line 120 coupled to the other end of the said series circuit formed by switches 58 and 62; thus completing an electrical circuit for energizing relay 64 and safety -switch heater 116.

Safety switch 112 cooperates with heater 116 to provide a predetermined time delay to turn off the burner in the event photocell 108 does not detect a ame from burner head 12 as will be later described.

Relay 64 being activated closes switch parts 122 and 128. Switch part 122 couples line 120 into control circuits while switch part 128 couples hot line 78 over line 130 to motor 24, to ignition transformer 132 (see FIG. l for physical location) and to other components as will hereafter become described. Motor 24 `begins loperating thereby rotating fan 26 (FIG. 1) to provide air to air chamber 18 through duct 20, fuel pump 34 to provide fuel to fuel valves 50, 52, and 54, and fan 30 to induce a draft from combustion chamber 32 through exhaust port 133 thence in stack `134. Ignition transformer 132 mounted as shown in FIG. l is coupled to ignition unit 136 as shown in FIG. 6 as a pair of spark electrodes physically located in burner head 12 as shown in FIG. 3. The ignition unit ignites any fuel-air mixtures in burner 12.

Fuel valve 50 is actuated simultaneously with switch part 128 closing, valve 50 being actuated by solenoid 139. Solenoid 139 receives power over line 140 coupled to line 130. Valve 50 is of the delayed action type, that is, the valve opens about four to five seconds after power is applied thereby permitting a later described combustion air stream to be established prior to fuel injection to the combustion chamber. This permits the motor 24 to reach full speed and thus fans 26 and 30 are providing good forced and induced drafts, respectively, to the combustion chamber 32 before the first fuel flows through burner head 12. Note that burner heads 14 and 16 cannot at this time receive any fuel.

The air flow from fan 26 to combustion chamber 32 is now described with reference to FIG. 3. Air duct has therein turning vanes i142 for turning the air supplied from fan 26 through duct 26 into air chamber 18 without turbulence. The thus provided air in chamber 18 is held at higher than atmospheric pressure by fan 26. Some of the air in chamber 18 enters tube 144 through ports 146, travels the length of said tube, and enters the combustion chamber 32 through ports 148 about fuel nozzle 150. The purpose of this air stream is to keep nozzle 150 relatively cool thereby insuring proper operation of the nozzle and does not appreciably add to the combustion air provided to combustion chamber `as now described. Each and every burner head has such an air tube arrangement to keep lthe respective fuel nozzles relatively cool.

Port 152 passes the major portion of the combustion air from chamber 18 to Iburner head 12, part entering burner cup 154 via ports 156 with the major portion of the combustion air stream of port .152 passing on the outside of said burner cup into the mixing area 158 to burner head 12. The burner heads are preferably designed to provide great air turbulence in area 158.

At least after the just described air streams are established, fuel valve (FIG. l or 6) opens and permits fuel from line 44 to pass through fuel line 168 (FIG. 6) to nozzle 150 and thence to be mixed in area 158 with the air stream just described to form a fuel-air mixture in combustion chamber 32. This described fuel mixture is ignited by element 136 (also see FIG. 6) to form flame 162.

Photocell 188 (FIG. 6) receives radiant energy in the form of light from frame 162 and provides an electrical signal to amplier 84 in the usual manner. Amplifier 84 suitably ampliiies said signal and provides energization of relay 68. Note that relay 82 (check relay) remains energized as heretofore described so long as power is continuously applied keeping switch part 106 continuously closed. As a result relay 68 is continuously energized as long as flame 162 is present. Thus switch parts 86, 88 and 90 are kept to the right hand position whenever the burner is operating.

With switch part 88 moved to the right hand or open position relay 164 is de-energized thereby closing switch 166. Therefore, when ame relay 68 is energized (switch part 88 is open) switch 166 is closed, coupling hot line 138 to bonnet controls 167 and 169. Note that when relay 68 is de-energized bonnet controls 167 and 169 do not have power applied to their respective switches and thus are electrically inoperable, therefore burner heads 14 and 16 which are controlled by said bonnet controls are also inoperable. Since relay 68 provides indication that flame 162 is present in the combustion chamber, it is obvious that bonnet controls 167 and 169 are operable onlyl when a flame has been established from burner head 12, thereby providing a safety lockout feature for burner heads 14 and 16.

An additional safety feature is provided by switch part 86 cooperating with safety switch heater 116. When relay 68 is energized and photocell 108 is not detecting Hame 162, then a current is flowing through heater 116. As soon as llame 162 is established and detected relay 68 opens switch part 86, thus prohibiting current ow from heater 116. The arrangement between heater 116 and switch 112 is that a predetermined time after current flows through heater 116 switch 112 opens thereby turning olf the fuel and air supplies by de-energizing relay 64. In this manner if flame 162 is not established within a predetermined time the burner will turn off thereby preventing combustion chamber from lling with fuel.

Bonnet controls 167 and 134 may be of the same type as bonnet control 60, excepting that the predetermined temperature at which their respective switch parts will actuate is a lower temperature. Therefore, when the bonnet (not shown) is at a low temperature, the switch parts of bonnet controls 167 and 169 will be closed,

thereby providing power to relays 168 and 170 resulting in a high rate of heat release in combustion chamber 32 as now described. This high rate of heat exchange serves to increase the bonnet temperature at a maximum rate.

When the switch part of control 167 is closed, power is applied to relay 168 thereby opening air valve 172 and closing switch 174. Switch 174 passes electrical current from line over line 176 to solenoid 178. Solenoid 178 actuates delayed action fuel valve 52 to provide fuel from fuel pump 34 over fuel line 180 to burner head 14.

Burner heads, or fuel burning devices, 14 and 16 are shown in dotted boxes in the lower center of FIG. 6. These elements are again shown at the upper left section of FIG. 6 and include the respective mechanical and electrical controls not shown in the lower portion of the drawing.

With reference now to FIG. 3 air valve 172 is shown in the closed position with plate 182 engaging housing rim 188. Plate 182 fastened to slidable sleeve 184 cooperates with port 186 as formed by rim 183 to comprise the said valve 172. Sleeve 184 is slidably mounted on tube 188 of burner head 14. Linkage 190 is suitably fastened to sleeve 184 and is coupled by a suitable linkage 192 (see FIGS. l and 4) to solenoid 168. Return spring 191 acts on linkage 198 to keep valve 172 closed when solenoid 168 is de-energized. When solenoid 168 is energized, linkage 192 is moved to the right as viewed in FIG. 4, thereby sliding sleeve 184 (FIG. 3) from the position indicated by numeral 194 to the position indicated by numeral 196 and compressing spring 191. Plate 182 is thus moved to the position indicated by numeral 198 thereby providing air passage 268 between air chamber 18 and burner head 14. After the just described action the air from chamber 18 passes both through ports 152 of burner head 12 and' through air valve 172 to burner head 14. About live seconds later time delay fuel valve 52 is opened and fuel is flowing through line 186 thence to nozzle 202, the said fuel mixing with the air from valve 172 in mixing area 284. This fuel mixture is expelled due to the velocities of the said fuel and air in head 14 through port 286 into combustion chamber 32 and is ignited by flame 162.

Nozzle 282 is held in place by nozzle adapter 202A on one end of which is formed a hexagon nut 202B. Small detents 283 formed in the side of tube 188 engage nut 282B to properly position nozzle 202 with respect to tube 188. Since tube 188 is round there are some small air spaces formed between the inside walls of said tube and the flat surfaces of hexagon nut 202B, thereby permitting the air Howing in said tube 188 to pass by nozzle 2012 as heretofore described.

Similarly when bonnet control 168 causes its switch part to close, relay is energized and switch 208 is closed to energize solenoid 210 and thus open fuel valve 54. Also relay 170 opens air valve 212 in the same manner as described for relay 168 to open valve 172 thereby permitting air to pass from chamber 18 to burner head .16 as also heretofore described for burner head 14. The resulting fuel mixture of head 14 is also ignited by flame 162.

As the tire in combustion chamber 32 increases the temperature in the bonnet (not shown) above the said predetermined temperatures, bonnet controls 167 and 169 cause their respective switch parts to open thereby de-energizing relays 168 and 170, respectively. The just described action closes fuel valves 52 and 54 and air valves 172 and 212 thereby causing the flames from burner heads 14 and 16, respectively, to be extinguished'. As the bonnet temperature again falls below the predetermined temperatures of the said bonnet controls the bonnet switches will again close and cause re-ignition of lthe llame of burner heads 14 and 16 in the manner just described. Thus the just described apparatus provides a modulating rate of heat exchange without turning the burner on and off. It is understood that burner head 16 bonnet thermostat 169 may have a lower predetermined temperature than burner head 14 bonnet thermostat 167, thus as the bonnet temperature may vary burner head 16 may alone be operated in conjunction with burner head 14, the requirement being solely the bonnet temperature.

It is obvious to those skilled in the art that the volume of air provided to air chamber 18 for burner heads 12, 14 and 16 is substantially constant, however, the need for the air varies depending on how many of the said burner heads are operating. As a result there still may be some ineiciencies introduced in burner operation. To provide yet more optimum fuel-air mixtures at all times this invention provides additional combustion air and draft controls as hereinbelow described. With ret'- erence again to FIG. 3 air bypass valve 214 is provided enabling part of the air in chamber 18 to escape to the atmosphere as indicated by arrow 216. Spring 218 is suitably anchored to the burner housing and is suitably fastened at point 220 to valve part 222. Valve part consists of arm 222A and plate 222B integrally mounted thereon, the whole valve part 222 being supported about hole 223A in the burner assembly 10 (see FIG. 5) at the juncture of parts 222A and 222B. Hole 223A is in a horizontal plane, arm 222A merely being inserted therethrough while the part 222B engages the burner assembly 10 to rotatably hold the assembly 222 in said hole 223A. Spring 218 exerts a pulling force on part 222 at point 220 thereby counterclockwise pivoting arm 222 about point 223 to the position shown thereby keeping valve 214 in the open position. Now when linkage 190 is moved by relay 168 (FIG. 6) as hereinabove described, arm extension 224 fastened to sleeve 184 engages valve part 222 at point 225, moving same to a closed position indicated by numeral 226. When valve part 222 is in position 226 no or negligible air escapes from chamber 18 through the valve to the atmosphere. When valve 172 is closed by relay 168 de-energizing and spring 191 acting on linkage 190, arm 224 is no longer engaged to part 222, thereby permitting spring 218 to close valve 214. Therefore, it is seen that when burner head 14 is not being operated part of the air in chamber 18 is passed to the atmosphere, whereas when burner 14 is being operated valve 172 is open while valve 214 is closed thereby switching the air ow from the atmosphere to burner head 14. By appropriately designing valve 214 the rate of air ow through port 152 of head 12 may be maintained at a substantially constant rate regardless of the operation of the other burner heads 14 and 16. The said constant rate of air flow insures optimum operation of burner heads 12, 14 and 16.

Further enhancement of the burner operation according to the teachings of this invention is provided by a draft retard valve 228 in combination with combustion air retard valve 230, such as illustrated in FIGS. 1 and 2 and each consisting of a rotatably mounted simple baille plate. Batlle plate or retard valve 228 is constructed with two tabs 228A and 228B, one on each of two 0pposing sides of said valve 228 as shown in FIG. 2. These said tabs are inserted into two round holes in stack 134 designed to receive same. After so inserting the tabs plate or valve 228 is rotatable about an axis lying between said tabs 228A and 228B.

It will be apparent to those skilled in the art that valve 228 may also be positioned at the inlet to the draft inducing blower. A suitable mechanism might be a moveable shutter, rotating about an axis at one edge of the blower inlet and operable to slidably cover all or a portion of the inlet opening.

These retard valves may be conveniently actuated by connecting a stiff steel or choke wire 232 (FIG. 3) from valve part 222 to swivel arm 234. Wire 232 passes through tubing 236 much in the fashion of a choke wire thereby permitting bi-directional mechanical linkage in a curvilinear fashion. Note that in FIG. 3 one end of wire 232 is shown entering box 238 while in FIG. 2 the other end of wire 232 is shown leaving box 238. It is understood that the wire parts shown in FIG. 3 and FIG. 2 are one and the same wire. Incidentally box 238 contains most of the wires forming the electrical interconnections between the components shown in FIG. 6 while box 239 contains several of the components as indicated in FIG. 4.

Valve part 222 in moving to position 226 causes wire 232 to actuate swivel arm 234 (FIG. 2) rotating said arm in the direction of arrow 240. Combustion air retard valve 230 is coupled to shaft 242 which is integrally formed with swivel arm 234, shaft 242 supported by simply being inserted through a small round hole 243 in opposing sides of duct 20. Therefore, when wire 232 rotates arm 234, valve 230 is rotated in a like direction. In FIG. 2 dotted lines 244 show valve 230 in the nonretard, i.e., open, position while line 246 shows valve 230 in the retard position. Wire 232 is connected to arm 234 at a point of radius with respect to shaft 242 such that position 246 is assumed by valve 230 when valve part 222 (FIG. 3) is in the open position, while position 244 is assumed when part 222 is in position 226. It is obvious from inspection of the figures how valve 230 retards the flow of combustion air through air duct 20 by providing a plate substantially covering the duct 20 cross section.

Swivel arm 234 is coupled by stiff `wire 248 to rotating linkage 250 consisting of arms 252 and 254 disposed at right angles to each other and separated by bearing rod 253. Bearing rod 253 is inserted in bearing 256 which is suitably mounted on the burner housing 258 to rotatably support linkage 250. Steel wire 260 couples arm 254 to draft retard valve 228. When valve 228 is in the position illustrated in FIG. 1, Le., vertical position, it is in the nonretard position while when in position indicated by dotted lines 262 valve 228 is in the retard position. Valve 228 cooperates with draft bafe 229 to control the induced draft. The mechanical linkage just described couples valve 230 to valve 228 such that as valve 230 rotates from position 246 (retard) to position 244 (open) the just described linkage causes the draft retard valve to move from closed position 262 to the illustrated open position rotating valve 228 in a clockwise direction.

It is to be remembered that sleeve 184 of FIG. 3 is moved as hereinabove described to close valve 214 only when solenoid 168 of FIG. 6 is actuated. Therefore, the just described retard valves 228 and 230 are actuated from the retard position to the non-retard position whenever burner head 14 is or is to be operated. Thus there is provided a greater forced and induced draft to combustion chamber 32 when higher rates of fuel injection are provided to it. In this manner this invention greatly enhances the operation of combustion chamber 32.

The preferred embodiment of this invention enables air bypass valve 214 to be actuated when either or both burners 14 or 16 are to be operated. With reference to FIG. 5 extension arm 224 on slidable sleeve 184 is seen in engageable position with respect to valve part 222. To the left of burner head 14 in head 16 there is provided a similar extension arm 264 mounted on a similar slidable sleeve 266. Linkage 268 similar to linkage 190 is connected to solenoid 170 (FIG. 6) as 190 is connected to 168. A spring member 270 causes linkage 268 to close valve 212 in the same manner as spring 191 closes valve 172. The operation and construction of vburner heads 14 and 16 are independent but identical, the only difference is in the bonnet controls 167 and 169 which may be manually set for different predetermined temperatures. The above described arrangement provides a sim-ple way of ensuring an adequate supply of combustion air for each burner head without control circuits for interlocking the burner heads 14 and 16 operation nor providing a separate solenoid for the air valves 214 and 230.

Thus there is provided burner Iapparatus accomplishing the various objects and advantages of this invention. It is understood that suitableV modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims.

Having now therefore fully illustrated and described my invention, what l claim to be new and desire to protect by Letters Patent is:

1. A fuel burning apparatus including first and second burner heads, each burner head having an axially elongated tubular fuel supply means including a fuel nozzle with an annular air passageway concentric therewith, an annular lair obstruction valve member movably mounted on said tubular fuel supply means for axial movement between a lfirst position yadjacent its air passageway for blocking same and a second position in non-blocking relation to its passageway, fuel supply means having fuel valve means in fluid communication respectively with the tubular fuel supply means including a fuel nozzle, operating control means including Va separate valve actuating means operatively associated with the valve member and each fuel valve means and having separate inter-locking means respectively for dea-ctivating the valve member actuating means when the first burner head fuel valve means is not actuated and for deactivating the second burner head fuel valve means when the valve member is in said first position, the annular air passageways being the only source of combustion air for the respective burner heads, and air control means responsively associated with the valve member for varying the air flow to the air passageways to keep a constant pressure thereat whereby a constant flow of combustion air is provided through each burner head when burning fuel.

2. A fluid fuel burner comprising Ia housing, first and second burner heads mounted in the housing and each having a fuel nozzle with an axially elongated center tube means and an annular air passageway concentrically disposed about the nozzle, an :annular sleeve axially slidably disposed over the second burner head tube means and having an annular valve member for blocking the second burner head air passageway when the sleeve is in a first axial position, the sleeve being movable to a second axial position for unblocking the passageway, :a fuel valve in fluid communication with each nozzle, temperature responsive control means operatively connected to the first burner head fuel valve for opening same, bonnet temperature responsive control means including a rod extending in parallel closely spaced apart relation to the tube means and operatively connected to the sleeve for axially urging the valve member toward the second axial position, second fuel valve control means including electrical interlocking means operatively connected to said rod for actuating the second burner head fuel valve means when the sleeve is in the second position, and combustion air supply means for supplying combustion air to the housing and including air bypass means operatively linked to said sleeve for closing as the sleeve is axially moved from the first position whereby the housing air pressure is kept relatively constant irrespective of the number of burner heads receiving combustion air.

3. A fuel burner comprising an air tight housing, first and second burner heads, each burner head having an axially elongated annular air intake means coaxially disposed about axially elongated fuel intake means inside the housing and fuel-air exhaust means outside the housing for passing fuel and air into a combustion chamber, first and second fuel valves respectively communicatively connected to the fuel intake means, air supply means communicatively connected to the housing for supplying combustion air thereto, an axially movable annular plate disposed around the second burner head fuel intake means inside the housing adjacent the second head air intake means for blocking air from flowing therethrough, actuating means operatively associated with the first fuel valve for opening same, burner control means including first burner head flame sensing means and operatively associated with the annular plate for axially urging same away from the air intake means of the second head and further operatively associated with the second fuel valve for opening same a predetermined time after urging the plate away from the second head air intake means, and open air bypass means on the housing and being engaged by the annular plate such that when the plate is axially urged away from the air intake means the bypass means is closed for keeping the housing air pressure substantially constant.

4. A fuel burner including first and second burner heads each having an annular air passageway coaxially disposed about a fuel tube, a fuel valve communicatively connected to each fuel tube, air supply means connected in fluid communicative relation to the air passageways, a normally closed air valve interposed between the supply means and the second burner head air passageway, a -normally open air valve in the air Asupply means for venting air outside of same, a normally air retarding valve in the supply means for retarding air flow therein, valve linking means operatively connected to all the air valves for simultaneously opening the normally closed and normally retarding valves and closing the normally open valve, burner control means operatively associated with the first burner head fuel valve for opening same and including flame sensing means adjacent the first burner head for sensing fuel burning thereby, and the control means including a single actuator connected to the linkage means for actuating the air valves after the flame sensing means has sensed fuel burning and having actuating means connected to the second burner head fuel valve for opening same a predetermined time after actuating the linkage means.

5. A combustion air supply for a multi stage burner assembly comprising a constant speed forced draft means, a combustion air chamber communicatively connected to said draft means for receiving air under pressure therefrom, a cluster of burner heads each having a fuel nozzle with a coaxial radially outward air passageway communicatively connected to the air chamber for transferring combustion air to each respective nozzle, an axially movable annular plate disposed adjacent the air chamber end of all air passageways but one and being movable between an air blocking and air passing positions with respect to the respective passageways, an air retard valve disposed in the chamber between the draft means and the burner heads, an air bypass valve disposed adjacent said plates and being in the air chamber for venting air to outside thereof, linking means connecting the retard valve to the bypass valve for opening the retard valve as the bypass valve is closed, control means including separate actuating means for independently moving said annular plates to the air passing position, and each plate having a radially extending arm for engaging the air bypass valve to close same when either of the plates are moved to an air passing position whereby the pressure :in the chamber remains substantially constant.

6. Apparatus as in the claim 5 further including variable induced draft means operatively connected to the air bypass valve for increasing the induced draft when `the bypass valve is closed.

7. A fuel burning apparatus including a first and at least a second burner head each having coaxial fuel air passage means, fuel supply means having first and at least a second fuel valve each respectfully communicatively connected to the burner heads, air supply means communicatively connected to said burner heads, a selectively operable air retard valve interposed between said air supply means and said burner heads for partially restricting the flow of combu-stion air to both burner heads, actuating means operatively connected to said second fuel Valve and to said air retard valve such that the said retard air valve is opened before said second fuel valve is actuated, control means operatively associated with the first fuel valve for opening it to pass fuel to said first burner head, air inlet valve means in said second burner head air passage -means for blocking air from entering, linking means for opening the air retard valve when said air inlet valve opens, and air inlet valve control means operatively associated with the first fuel valve means for opening said air inlet valve only after the fuel valve means has been passing fuel to the first burner head and a arne established at said first burner head.

8. A fuel burning apparatus including a first and at least a second burner head, a combustion chamber cornmunicatively connected to said burner heads, fuel supply means having control means and first and at least second fuel valve means, air supply means having a `first normally closed air retard valve, an air chamber in fluid communication with the air supply means, a normally closed air valve communicatively connecting said air chamber to said second burner head, a normally open air valve communicatively connecting said air chamber to the atmosphere, actuating means operatively associated with the air valve for actuating all of said valves to the other than normal position, the said iirst fuel valve means being in iiuid communication with the said first burner head, said air chamber being continuously in uid communication with iirst burner head, the said -rst burner head exhausting the fuel and air into said common combustion chamber for burning, the second fuel valve means being in fluid communication with the second burner head, said actuating means being connected to the control means to permit energization of said second fuel valve means only concurrently to simultaneous actuation of said air valves such that the air pressure inthe air chamber remains substantially constant.

9. In apparatus of the class above described, a plurality of fuel burning devices each having coaxial air and fuel passages; a source of fuel connected to each of said fuel passages through a plurality of fuel valve means corresponding in number to said plurality of fuel burning devices; a source of air supply connected to each of said air passages, a plurality of air valve means controlling air flow from said source to said passages and corresponding to the number of said plurality of fuel burning devices, one of said air valve means being normally open; further variable air valve means connected to said air supply source and operable to maintain a substantially constant said air supply; means interlocking the fuel valve means connected to one of said fuel burning devices and said air valve means to prevent actuation thereof until after a flame has been established at the one of said fuel burning devices; and further means connecting each of said air valve means to corresponding fuel valve means so that each of said fuel valve means is actuated only upon the opening of said air valve means.

References Cited in the tile of this patent UNITED STATES PATENTS 821,419 Kemp May 22, 1906 1,493,919 Cunningham `May 13, 1924 1,637,820 Hawkins Aug. 2, 1927 2,237,041 Schreuder Apr. l, 1941 2,362,045 Bliss Nov. 7, 1944 2,390,806 Nagel Dec. 11, 1945 

